Battery maintenance

[cbr954rr]

Is there anything we can be doing to help the battery last?

[jj2me]

- Avoid high battery heat. Here and here is one person's experience that he gets no battery degradation keeping battery temps maxed at 105°F (40.5°C) or even 102°F (39°C), vs. high degradation when relying on the Energi to automatically cut off EV at its cutoff temp of 113°F (45°C).  Another person never charges in the summer in his hot climate, just lets it go to a reading of 0% charged, and has had insignificant degradation.  You can monitor this with an OBDII dongle and an app like FORScan Lite.

 

- Especially don't mix 100% charge level and high heat.  Charge to 100% just before you'll be driving.  Viewgraph 18 here says "Huge calendar lifetime benefit w/ delayed charging." 

 

- Try to keep a reasonable C-rate value when discharging and charging.  Limiting to 1C is ideal, but not always practical.  C-rate is the rate at which you'll deplete the battery in one hour.  Using a 22-mile (35-km) range on the 5.6 kWh we can charge, that would equate to about 30 miles (48 km) for our full capacity of 7.6 kWh.  So a C-rate of 1 is driving 30 mph (48 km/h); 2 if driving 60 mph (96 km/h).  For charging, a Level 1 charge is hypothetically better than a Level 2 charge, but we have no data nor any anecdotes that this is true for the Energi, and you'll probably be better about delayed charging behavior with the quicker-charging Level 2.

 

- Try to keep charge level in the range of 20% to 80% as much as possible.  See the DOD (depth of discharge) and SOCmax (max state of charge) slides in the above linked viewgraphs. Although the person who lets his charge level go to 0% indicated (there's still some charge left for safety reserve and for hybrid operation) has experienced so little degradation that we could think going to an indicated 0% causes no harm.

Edited April 25, 2019 at 03:21 PM by jj2me

[jsamp]

Agree with jj2me and will add a little.  

 

High "C" rate is a danger in the Energi's.  Flooring it in EV will pull >4C rate which is way too high.  But high demand on the battery can come from multiple sources at the same time as well.  Driving on EV with the heater cranked can elevate drain rate above 2C, especially at freeway speeds.  

 

I do drive at 65MPH in EV, but do not accelerate to 65 using EV.  The difference equals over taxing the battery.  So far my battery is in great shape at 65K miles.

[cbr954rr]

Thanks for the replies everyone

[bdginmo]

I'll ditto the high heat thing. Avoiding charging and using the HVB on hot summer days. At 65k miles I only have about 5% degradation. I pretty much stop charging altogether during the summer months.